The present invention relates to the field of digital imaging, in particular to the field of estimating geometrical properties of an anatomical object. According to the present invention, geometrical properties are automatically measured and geometrical properties which have a definition based on sub-parts of the object are derived. To do this, additional geometrical information is integrated into a surface model. Geometrical properties are included into the surface model by identifying and labelling sub-parts of the surface model and fitting geometric primitives to these sub-parts. This advantageously allows to identify these sub-parts on an unseen object surface and to automatically extract relevant geometric properties.